Evidence of a counter‐current heat exchanger in the ray, Mobula tarapacana (Chondrichthyes: Elasmobranchii: Batoidea: Myliobatiformes)

A vascular network, or rete, has been found in the pectoral fin of the mobulid ray, Mobula tarapacana. This rete appears to be a counter‐current heat exchanger which, in conjunction with a high level of red muscle, indicates that this ray is warm‐bodied. Preliminary results on other closely related rays indicate that retia may be more common amongst the rays than previously thought.